1. Animal agriculture is the number one driver of deforestation and species extinction in the Amazon rain forest.
2. Contrary to pseud0-intellectual arguments against monoculture, most soy and corn grown today is being fed to "food animals" so world veganism would NOT be "less sustainable due to monoculture" I mean come on it's like these people need help tying their shoes or smthng
3. Contrary to pseudo-intellectual arguments about B12, the bulk of cobalt being mined right now is fed to livestock. Cattle is the number one waste dump of B12 supplementation, followed by other farmed animals like chickens. Meat eaters can cry about B12 all day long if they want, but the world has been raped by animal ag for centuries, and pretty much nobody is getting their B12 "naturally" so LESS B12 would actually be needed by world veganism.
4. Animal agriculture is the number one hog of fresh water and land, as well as being comparable to fossil fuels in terms of carbon and methane emissions.
5. Animal torture observed in children or teens is seen as a trait of sociopathy or psychopathy, but observed in factory farm workers or first world capitalist consumers or scientific testing is somehow socially acceptable. Can you say cognitive dissonance? I knew you could!
6. It's the 21st century. There's really no excuse why you "need" animal products unless you literally live on rocky terrain in a developing country, and in that case, you could still be a vegetarian.
7. Animal product consumption in the Western world is literally a driver of world starvation, stealing food from the mouths of hungry children.
8. A pig is a rat is a dog is a boy.
9. Adam and Eve were vegan. Most major world religions have some major ethic surrounding veganism, vegetarianism, or preventing animal cruelty. Anyone who says they eat steak because of their religion probably aren't actually very spiritual people.
10. Health.